Conventionally, in order to change the operation state of the compressor for adjusting the temperature of a refrigerator or an air conditioner, since the speed of the compressor driven by a conductive motor is not change, the compressor should be driven by switching power on or off.
In other words, if a prescribed temperature is satisfied, the power is turned off to stop the compressor. After a predetermined time lapses so that the temperature deviates the prescribed temperature, the power is again turned on to operate the compressor so that the temperature becomes satisfiable. This is called a power on/off controlling method.
Also, there is another method of controlling the temperature of the compressor by changing the operative frequency thereof using an inverter, by which if a prescribed temperature is satisfied, the frequency is reduced to operate a compressor slowly. That is to say, if a detected temperature deviates from the predetermined temperature, the frequency is increased to operate the compressor fast so that the temperature is satisfied.
In this manner, the frequency is varied depending on the change of temperature around the prescribed temperature to control the operation of the compressor.
However, the conventional compressor controlling apparatus has the following problems.
First, in the power on/off controlling method, due to repeated drive and stop operation of the motor for driving the compressor, the life of the motor is shortened, and the temperature change is severe.
Next, the compressor controlling method using an inverter involves a problem in that the inverter is expensive, which leads to the cost rise of products.